1. Technical Field
The present invention relates to a vehicle occupant protection apparatus including an air bag inflator. In particular, the present invention relates to the deactivation, for safety reasons, of the second stage of a dual stage air bag inflator, in the case when only the first stage is actuated to inflate the air bag.
2. Description of the Prior Art
An inflator for an inflatable vehicle occupant protection device, such as an air bag, includes a source of inflation fluid. The source of inflation fluid may be an ignitable material which, when ignited, rapidly generates a large volume of inflation fluid in the form of gas. The inflator may alternatively contain a stored quantity of pressurized inflation fluid, or a combination of pressurized inflation fluid and ignitable material for heating the inflation fluid.
Some inflators are of the xe2x80x9cdual stagexe2x80x9d type and include two separate, independently actuatable inflation fluid sources (xe2x80x9cstagesxe2x80x9d). The two inflation fluid sources can be actuated simultaneously or at different times to tailor the rate and volume of flow of inflation fluid out of the inflator. In some cases, only one of the inflation fluid sources is actuated, for example, when a relatively low fluid flow rate is desired. In these cases, the second inflation fluid source remains active after deployment of the air bag. It is desirable, for safety reasons, to deactivate the second inflation fluid source when it has not been used to inflate the air bag.
The present invention is an apparatus for helping to protect a vehicle occupant. The apparatus comprises an inflatable device. The apparatus comprises a primary inflation fluid source and a secondary inflation fluid source actuatable independently of each other. The apparatus further comprises means for actuating the primary inflation fluid source to inflate the inflatable device to help protect the vehicle occupant without actuating the secondary inflation fluid source. The apparatus also comprises means for sensing the position of the vehicle occupant subsequent to actuation of the primary inflation fluid source and for providing an output signal. The apparatus further includes means for actuating the secondary inflation fluid source in response to the output signal.